This work is focused on the study of the formation of an alumina (aluminum oxide) layer by double anodizing of aluminum. From this controlled oxidation method, a nanostructured porous layer with hexagonal cells was obtained. Ordered porous structures with 40-52 nm pore diameter were obtained by applying oxalic acid and a voltage-controlled procedure. The morphology of the surface and cross-section of the samples was analyzed by electron microscopy (Scanning and transmission). Finally, using this porous alumina as a template, Ni nanowires were obtained by electrochemical growth of the metal into the pores.